Psychrobacter sp. XL111, a novel bacterial species from hadal amphipods: genomic insights into environmental adaptation and biotechnological potential.

The hadal zone presents one of the most extreme environments on Earth. While amphipods dominate this realm, the adaptive mechanisms of their resident gut microbiota are not fully understood, which is essential both for understanding the limits of life and for unlocking novel microbial resources. This study investigates Psychrobacter sp. XL111, a novel bacterial species isolated from the gut of hadal amphipods, to elucidate its survival strategies and biotechnological potential. Pan-genome analysis confirms the high genomic plasticity of this genus and highlights the genomic innovations in genes related to environmental adaptation. Genomic analysis revealed specialized adaptations to the deep-sea niche, including expansions in signal transduction systems, pathways for degrading complex organics and the capacity to synthesize stress-resistant compounds. A notable loss of oligosaccharide transporters alongside an enrichment of glycosyltransferases suggests a distinctive evolutionary reconfiguration of carbohydrate metabolism. Functional characterization confirmed that the strain produces an exopolysaccharide with potent radical-scavenging activity, underscoring a key mechanism for mitigating oxidative stress. Our results position hadal micro-organisms as a valuable source of novel enzymes and bioactive molecules for industrial and biomedical applications.